Demand disinfectant iodinated resins have been used in a variety of applications. For instance, iodinated resins may be used to sterilize fluids such as water, air, blood and other bodily secretions by devitalizing microorganisms such as fungi, protozoan, bacteria and viruses that may be present in the fluid. Additionally, iodinated resins can be used in wound dressings, disinfectants, filters, clothing, fibers, facemasks, polymers, non-polymeric structures and coatings.
Numerous manufacturing processes for making demand disinfectant iodinated resins are disclosed in the prior art. U.S. Pat. No. 5,639,452 to Messier, the content of which is incorporated herein by reference, discloses a disinfectant substance comprising iodine impregnated ion exchange resin and a process for the preparation thereof. The Messier patent discloses that this disinfectant is a demand-type broad spectrum resin-polyiodide disinfectant useful in sterilizing fluids, and particularly a polyiodide disinfectant in which the iodine is more tenaciously associated with the resin than with previously known disinfectants, such that it leaves behind nondetectable or otherwise acceptable residual diatomic iodine in treated fluids. The demand disinfectant iodinated resins disclosed in Messier are generally formed by contacting a strongly basic anionic resin with an aqueous solution of iodine and potassium iodide under conditions of high temperature and pressure. Iodinated resin beads (Triosyn®) are made by Triosyn Research Inc., a division of Triosyn Corporation of Vermont, USA.
U.S. Pat. No. 5,431,908 to Lund also teaches a method of preparing halide-impregnated ion exchange resins useful in purifying fluids such as water. The method involves circulating an effective amount of polyhalide salt carrier solution between an effective amount of elemental iodide and a strong base anion exchange resin until all of the resin is converted to the polyhalide form.
The processes disclosed in Messier and Lund are useful in preparing iodinated resin granules or beads with diameters ranging from 0.2 mm (200 microns) to 0.8 mm (800 microns). However, smaller particulates are required for the production of some filters, polymeric or non-polymeric extrusions, wound dressings, fibers and coatings Moreover, use of iodinated resins in coatings and in aerosols requires smaller particulates. It is possible to produce small iodinated resin particulates of the desired size by grinding the beads produced by the method described in Messier. In addition, U.S. Pat. No. 6,562,885, to Moorehead, the content of which is incorporated herein by reference, discloses a method of manufacturing smaller iodinated resin particulates, on the scale of 0.1-300 microns. Moorehead starts with iodinated resin beads, as prepared in Messier, and grinds them into smaller particulates. After selecting particulates of the appropriate size, the particulates may be re-iodinated by contacting them with an aqueous solution of iodine and potassium iodide under conditions of high temperature and pressure.
The methods described above for producing micronized iodinated resin particulates have several disadvantages. The pieces of particulate iodinated resin formed following the grinding of the larger iodinated resin beads have different iodine content because the large beads cannot be homogeneously iodinated from the surface to the core of the sphere of the bead. In the larger beads, there is less iodine in the center of the bead than on the edges of the bead. As a result, the individual particulates, after grinding of the larger resin bead, have differential amounts of iodine. Although the particulates can be re-iodinated, as described in Moorehead, the re-iodination process does not produce uniformly iodinated particulates. While the iodine content of the initially less impregnated particulates is increased, the iodine content of the particulates that were already optimal prior to re-iodination is increased as well. Additionally, the process results in a considerable amount of iodine waste, which is environmentally toxic.
Being that the percent iodine content of a resin determines the toxicological properties and the biocidal properties thereof, such nonuniformity translates into a large fluctuation of the biocidal performances of individual particulates. As a result, when the particulates are incorporated into filters, polymeric extrusions or coatings, for example, the resultant product (e.g., filter, wound dressing or wipe) may not behave uniformly. Consequently, if iodinated resin particulates are incorporated into a filter, it is possible that microorganisms migrating through areas of the material containing particulates of low iodine content will not be devitalized while microorganisms migrating through areas of the filter containing areas of high iodine content will be devitalized. Moreover, being that the particles are dispersed in a medium having an area much larger than the iodinated resin particulates, different areas of the medium may have different toxicological properties.
In addition to problems with nonuniformity described in the preceding paragraphs, the methods described in Messier, Lund and Moorehead are time-consuming, technologically challenging and costly. For instance, methods described in Messier and Moorehead necessitate the use of a step for iodine impregnation with requires water or other liquids, or batch blending. In particular, prior art methods require the use of an aqueous sludge of iodine and potassium iodide. Working with such a sludge is complicated, particularly when dealing with small resin particulates. Moreover, in order to obtain a dry iodinated powder to be used in filters, coatings, polymeric and non-polymeric extrusions, the additional step of drying the water content is required. Generating smaller particulates is particularly challenging. Using the Moorehead process, for instance, requires two iodination steps, one to produce the larger beads and one to re-iodinate the smaller particulates after grinding. Hence, the batch process and drying steps must be performed twice. When a specific range of particulate size is required a sieving step is also required. Accordingly, the multiple manufacturing steps are extensive and cost-prohibitive.
Furthermore, the prior art manufacturing processes may have negative environmental consequences owing to the loss of iodine to the environment. Processes requiring multiple iodination steps are particularly unfriendly to the environment. Additionally, the use of water in the prior art processes generates considerable toxicological waste because fluid containing iodine are generated.
Hence, there exists a need to develop a new manufacturing process to generate iodinated resins that is technologically simpler, less costly, yielding a more biologically potent and more environmentally friendly resin. Additionally, there exists a need to generate small iodinated resin particulates that have a uniform content of iodine and thereby can be applied to antimicrobial products including filters, coatings and wound dressings.